U.S. patent application number 09/455318 was filed with the patent office on 2002-05-02 for semiconductor device.
Invention is credited to MIMURA, CHIKAYA, NAKASHIMA, KAORU, SAKATA, SEIICHIRO.
Application Number | 20020050640 09/455318 |
Document ID | / |
Family ID | 12862592 |
Filed Date | 2002-05-02 |
United States Patent
Application |
20020050640 |
Kind Code |
A1 |
NAKASHIMA, KAORU ; et
al. |
May 2, 2002 |
SEMICONDUCTOR DEVICE
Abstract
A semiconductor device capable of preventing moisture from
entering into a package and also capable of preventing peeling
between a pad and the package from occurring. The semiconductor
device comprises grooves formed on a semiconductor element mounting
surface of the pad to surround the semiconductor element, plated
portions formed on only a ground bond area of the semiconductor
element mounting surface of the pad, a thin portion formed on an
entire peripheral edge portions on the back of the pad, and thin
portions formed at portions which connect with the pad, on backs of
support bars extending from the pad.
Inventors: |
NAKASHIMA, KAORU; (FUKUOKA,
JP) ; MIMURA, CHIKAYA; (FUKUOKA, JP) ; SAKATA,
SEIICHIRO; (FUKUOKA, JP) |
Correspondence
Address: |
VARNDELL & VARNDELL PLLC
106-A South Columbus Street
ALEXANDRIA
VA
22314
US
|
Family ID: |
12862592 |
Appl. No.: |
09/455318 |
Filed: |
December 6, 1999 |
Current U.S.
Class: |
257/737 ;
257/E23.037 |
Current CPC
Class: |
H01L 2224/49171
20130101; H01L 2924/01029 20130101; H01L 2924/01047 20130101; H01L
2924/181 20130101; H01L 2924/19107 20130101; H01L 2224/48247
20130101; H01L 2924/00014 20130101; H01L 2224/73265 20130101; H01L
2224/48091 20130101; H01L 2924/00014 20130101; H01L 2924/01015
20130101; H01L 2224/73265 20130101; H01L 2924/01077 20130101; H01L
2224/49175 20130101; H01L 2924/01078 20130101; H01L 2924/351
20130101; H01L 2924/351 20130101; H01L 2924/01023 20130101; H01L
2224/32245 20130101; H01L 2924/01028 20130101; H01L 2924/181
20130101; H01L 2224/4911 20130101; H01L 2924/01006 20130101; H01L
2924/00 20130101; H01L 2224/48257 20130101; H01L 2224/48257
20130101; H01L 2224/32245 20130101; H01L 2924/00 20130101; H01L
2924/00 20130101; H01L 2224/05599 20130101; H01L 2224/32245
20130101; H01L 2924/19107 20130101; H01L 2224/48247 20130101; H01L
2224/48247 20130101; H01L 2224/32245 20130101; H01L 2924/00012
20130101; H01L 2224/48247 20130101; H01L 2924/00 20130101; H01L
2224/48247 20130101; H01L 2924/00 20130101; H01L 2224/49109
20130101; H01L 2924/00014 20130101; H01L 2224/45099 20130101; H01L
24/49 20130101; H01L 2924/00 20130101; H01L 2224/49109 20130101;
H01L 2224/48091 20130101; H01L 2924/01074 20130101; H01L 2224/73265
20130101; H01L 24/48 20130101; H01L 23/49503 20130101; H01L
2224/4911 20130101; H01L 2924/01005 20130101; H01L 2224/49171
20130101; H01L 2224/05554 20130101; H01L 2224/49175 20130101; H01L
2224/73265 20130101; H01L 2924/00014 20130101 |
Class at
Publication: |
257/737 |
International
Class: |
H01L 023/495 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 26, 1999 |
JP |
50567/1999 |
Claims
What is claimed is:
1. A semiconductor device in which a back of a pad for mounting a
semiconductor element is exposed to an outside of a package,
comprising: grooves formed on a semiconductor element mounting
surface of the pad to surround the semiconductor element; plated
portions formed on only a ground bond area of the semiconductor
element mounting surface of the pad; a thin portion formed on an
entire peripheral edge portions on the back of the pad; and thin
portions formed at portions, which connect with the pad, on backs
of support bars extending from the pad.
2. The semiconductor device according to clam 1, wherein the thin
portion formed on the entire peripheral edge portions on the back
of the pad has a thickness of at least 40% of a thickness of a
non-thin portion.
3. The semiconductor device according to claim 1 or 2, wherein the
grooves formed on the semiconductor element mounting surface of the
pad to surround the semiconductor element are provided in plural
numbers respectively along the edges of the pad with spaces
therebetween.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a semiconductor device
which is configured to expose the back of a semiconductor element
mounting pad to the outside of a package.
[0003] 2. Description of the Related Art
[0004] In order to favorably release heat and electromagnetic noise
generated as semiconductor element B is made to have a large size
and large capacity, and to achieve thinning of package P,
semiconductor device A shown in FIG. 5 has pad C which mounts the
semiconductor element B and which is down set and the back of the
pad C is exposed to the outside of package P.
[0005] In the semiconductor device A, the semiconductor element B
and leads L, L, . . . are connected by bonding wires W, and in
order to use the pad C as a ground, the entire surface of the pad C
is plated with a noble metal such as Ag (silver), and the
semiconductor element B and the pad C are bonded by bonding wires
(ground bonding wire) G for grounding.
[0006] Meantime, the aforesaid semiconductor device A has a
disadvantage that moisture is easy to enter into it through
boundary part V between the pad C and the package P because the pad
C is exposed to the outside of the package P, and when moisture
reaches a semiconductor element-mounting surface of the pad C and
evaporated or expanded as the semiconductor device A is heated, a
popcorn crack might be caused.
[0007] It also has a disadvantage that since the pad C of the
semiconductor device A has its large area exposed to the outside of
the package P, it is directly affected by heat when the
semiconductor device A is exposed by a heat cycle of heating and
cooling to cause a gap at the boundary part V between the pad C and
the package P due to a difference in heat expansion rate, and
moisture is allowed to enter through the gap.
[0008] Furthermore, there is a disadvantage that the noble
metal-plated surface on the entire surface of the pad C is poor in
intimate contact with the package (sealing resin) P as compared
with a non-plated surface, so that when the semiconductor device A
is exposed to a heat cycle, broad peeling is caused between the pad
C and the package (sealing resin) P to break any of the bonding
wires (ground bonding wire) G.
[0009] There is also a disadvantage that when epoxy resin-based
adhesive agent F used to fix the semiconductor element B to the pad
C is precipitated to the surface of the pad C due to heating to
form a bleed layer, broad peeling is also caused between the pad C
and the package (sealing resin) P to break any of the bonding wires
(ground bonding wire) G.
[0010] In view of the aforesaid circumstances, it is an object of
the present invention to provide a semiconductor device which can
prevent moisture from entering the package and also can prevent
peeling between the pad and the package from occurring.
SUMMARY OF THE INVENTION
[0011] The semiconductor device of claim 1 according to the present
invention is a semiconductor device in which a back of a pad for
mounting a semiconductor element is exposed to an outside of a
package, comprising: grooves formed on a semiconductor element
mounting surface of the pad to surround the semiconductor element;
plated portions formed on only a ground bond area of the
semiconductor element mounting surface of the pad; a thin portion
formed on an entire peripheral edge portions on the back of the
pad; and thin portions formed at portions, which connect with the
pad, on backs of support bars extending from the pad.
[0012] By configuring as described above, an unexpected gap can be
prevented from being formed at the boundary between the pad and the
package, and a route of moisture at the boundary between the pad
and the package becomes long, so that moisture can be prevented
from entering into the semiconductor element-mounting surface of
the pad, and a popcorn crack can be prevented from occurring.
[0013] And, by configuring as described above, an adhesive agent
does not flow to expand to all the area of the semiconductor
element-mounting surface of the pad, and plated portions having
poor adhesion with the package are formed on only a minimum ground
bond area. Therefore, extensive peeling between the package and the
pad can be prevented, and bonding wires are prevented from being
broken.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIGS. 1(a) and 1(b) are plan diagrams showing a
semiconductor device according to the present invention;
[0015] FIGS. 2(a) and 2(b) are bottom diagrams showing a
semiconductor device according to the invention;
[0016] FIGS. 3(a), 3(b) and 3(c) are respectively sectional
diagrams taken on lines a-a, b-b and c-c of FIG. 1(b);
[0017] FIGS. 4(a) and 4(b) are a plan diagram and a side sectional
diagram showing another embodiment of the semiconductor device
according to the invention; and
[0018] FIGS. 5(a), 5(b) and 5(c) are a plan diagram, a bottom
diagram and a side sectional diagram showing a conventional
semiconductor device.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0019] The present invention will be described in detail with
reference to the accompanying drawings.
[0020] As shown in FIG. 1 through FIG. 3, semiconductor device 1 of
the present invention is a DIL (dual inline) type semiconductor
device which has a plurality of leads 3, 3, . . . protruded from
either side of package 2, and back 4b of pad 4 is exposed at bottom
2b of the package 2.
[0021] Semiconductor element 5 is mounted (adhered) at the center
area of semiconductor element-mounting surface 4a of the pad 4 with
an epoxy resin-based adhesive agent and electrically connected to
the respective leads 3 (plated portions 3m) through bonding wires
W.
[0022] Portions 4m, 4m plated with a noble metal such as Ag
(silver) are formed on the semiconductor element-mounting surface
4a of the pad 4, and the semiconductor element 5 mounted on the pad
4 is electrically connected (ground bonded) to the respective
plated portions 4m, 4m through bonding wires (ground bonding wires)
G.
[0023] In this embodiment, particular leads 3 and the plated
portions 4m of the pad 4 are also bonded (ground bonding) through
the bonding wires.
[0024] The plated portions 4m, 4m are not formed on the entire area
of the semiconductor element-mounting surface 4a of the pad 4 but
on a part of the semiconductor element-mounting surface 4a,
specifically on only a minimum ground bond area required for
connecting the bonding wires G.
[0025] Grooves 4A, 4A, 4A, 4A are formed on the semiconductor
element-mounting surface 4a of the pad 4 to surround the
semiconductor element 5 mounted on the pad 4.
[0026] Stepped thin portion 4B is formed along the entire edge of
the back 4b of the pad 4.
[0027] A pair of support bars 6, 6 extended from the pad 4 have
thin portions 6A, 6A formed on their backs 6b used as bonding
portions for connection with the pad 4, and the thin portions 6A
are assimilative with the thin portion 4B.
[0028] The semiconductor device 1 described above is produced by
the following steps.
[0029] A lead frame is shaped from a copper-based or
ion-nickel-based material by etching.
[0030] At this time, the respective grooves 4A, 4A, . . . on the
semiconductor element-mounting surface 4a of the pad 4 and the thin
portion 4B on the back 4b of the pad 4 are also formed by
etching.
[0031] The lead frame can also be formed by stamping by a press,
and when the lead frame is formed by the press, the grooves 4A and
the thin portion 4B of the pad 4 can also be formed by pressing
such as coining at the same time.
[0032] After forming the lead frame, the plated portions 4m, 4m of
a noble metal such as Ag (silver) are formed on the necessary area
(ground bond area) of the semiconductor element-mounting surface 4a
of the pad 4, and the plated portions 3m, 3m, . . . are formed on
the necessary areas of the respective leads 3, 3, . . .
[0033] Then, the support bars 6, 6 of the lead frame are depressed
to down set the pad 4 at a lower part.
[0034] At this time, the thin portions 6A, 6A of the support bars
6, 6 are also formed by coining by means of a press when the pad 4
is down set.
[0035] It is to be understood that the down set of the pad 4 and
the forming of the thin portions 6A of the support bars 6 can be
performed independently by a separate process.
[0036] The thin portions 6A of the support bars 6 can also be
formed by etching instead of pressing.
[0037] The thin portions 6A of the support bars 6 and the thin
portion 4B of the pad 4 are desirably set to have a depth of at
least 40%, preferably 60% or more, of a thickness of a base
material.
[0038] After down setting the pad 4, the semiconductor element 5 is
mounted (adhered) on the semiconductor element-mounting surface 4a
of the pad 4, the semiconductor element 5 and the respective leads
3, 3, . . . are mutually connected by the bonding wires W, and the
semiconductor element 5 and the pad 4 are connected (ground
bonding) by the bonding wires (ground bond wire) G.
[0039] With the back 4b of the pad 4 exposed, the package 2 is
formed by molding with the sealing resin, the respective leads 3,
3, . . . , and the support bars 6, 6 are separated from the lead
frame to complete the semiconductor device 1.
[0040] In the semiconductor device 1 configured as described above,
the thin portion 4B of the pad 4 and the thin portions 6A of the
support bars 6 are covered with the sealing resin of the package 2
as shown in FIG. 3, and an entering route of moisture at the
boundary V between the pad 4 and the sealing resin becomes long, so
that moisture can be prevented from entering the semiconductor
element-mounting surface 4a of the pad 4.
[0041] When the semiconductor device 1 configured as described
above is exposed to a heat cycle of heating and cooling, the
grooves 4A, 4A, . . . formed on the pad 4 serve to absorb a stress
applied to the pad 4 so to prevent the pad 4 from being deformed.
Thus, an unexpected gap is prevented from being formed at the
boundary V between the package (sealing resin) 2 and the pad 4, and
moisture can be prevented from entering the semiconductor
element-mounting surface 4a of the pad 4.
[0042] As described above, the semiconductor device 1 configured as
described above can prevent moisture from entering the
semiconductor element-mounting surface 4a of the pad 4, and a
so-called popcorn crack can be prevented from occurring in the
device 1.
[0043] In the semiconductor device 1 having the aforesaid
structure, even when the adhesive agent fixing the semiconductor
element 5 to the pad 4 is flown out by heating, it is caught by the
grooves 4A, 4A, . . . formed on the semiconductor element-mounting
surface 4a of the pad 4, so that the adhesive agent does not spread
to fully cover the semiconductor element-mounting surface 4a. Thus,
extensive peeling between the package (sealing resin) 2 and the pad
4 can be prevented.
[0044] Extensive peeling between the package (sealing resin) 2 and
the pad 4 can also be prevented from occurring because the plated
portions 4m, 4m having poor intimate contact with the package
(sealing resin) 2 in the semiconductor device 1 having the
aforesaid configuration are formed on only the minimum ground bond
area of the semiconductor element-mounting surface 4a of the pad
4.
[0045] As described above, the semiconductor device 1 can prevent a
problem that the bonding wires G are broken because the extensive
peeling between the package (sealing resin) 2 and the pad 4 can be
prevented.
[0046] FIG. 4 shows another embodiment of the semiconductor device
according to the present invention, wherein grooves 14A, 14A, 14A,
14A are formed on pad 14 of semiconductor device 10 to surround
semiconductor element 15 mounted on the pad 14, and outside grooves
14C, 14C, 14C, 14C are also formed along the edge of the pad
14.
[0047] The configuration of the aforesaid semiconductor device 10
is the same as that of the semiconductor device 1 shown in FIG. 1
through FIG. 3 excepting the outside grooves 14C, 14C, . . . of the
pad 14. Therefore, the reference numerals used in FIG. 1 through
FIG. 3 are also used in FIG. 4 with 10 added to indicate the
elements having the same functions as those of the semiconductor
device 1, and detailed descriptions of the same elements are
omitted.
[0048] In the semiconductor device 10 configured as described
above, the outside grooves 14C, 14C, . . . are formed on
semiconductor element-mounting surface 14a of the pad 14, so that
an entering route of moisture from back 14b of the pad 14 becomes
longer than in the semiconductor device shown in FIG. 1 through
FIG. 3, and moisture is caught by the outside grooves 14C, 14C, . .
. and can be prevented from entering into the semiconductor
element-mounting surface 14a of the pad 14.
[0049] When exposed to a heat cycle of heating and cooling, the
grooves 14A, 14A, . . . and the outside grooves 14C, 14C, . . . of
the pad 14 serve to absorb a stress applied to the pad 14 so to
suppress the pad 14 from being deformed. Thus, an unexpected gap
can be prevented from being formed at a boundary between package 12
and the pad 14, and moisture can be prevented from entering the
semiconductor element-mounting surface 14a of the pad 14.
[0050] According to the semiconductor device 10 configured as
described above, a so-called popcorn crack can be prevented from
occurring because moisture can be prevented from entering the
semiconductor element-mounting surface 14a of the pad 14.
[0051] Even if the adhesive agent used to fix the semiconductor
element 15 to the pad 14 is flown out due to heating, it can be
caught by the grooves 14A, 14A, . . . formed on the pad 14, so that
the adhesive agent is not expanded to the entire area of the
semiconductor element-mounting surface 14a, and extensive peeling
between the package 12 and the pad 14 can be prevented.
[0052] Plated portions 14m, 14m having poor intimate contact with
the package 12 are formed on only the minimum ground bond area of
the semiconductor element-mounting surface 14a of the pad 14, so
that extensive peeling between the package 12 and the pad 14 can be
prevented from occurring.
[0053] Thus, according to the semiconductor device 10 configured as
described above, a problem that bonding wires G are broken can be
prevented from occurring because the extensive peeling between the
package 12 and the pad 14 is prevented.
[0054] To examine the reliability of the semiconductor device,
there is a test that the semiconductor device is placed in a
chamber at a high humidity to damp the package and subjected to a
thermal stress by an IR (infrared rays) reflow device to check the
occurrence of a crack and peeling in the package. And, it is
apparent that the semiconductor device 1 and the semiconductor
device 10 in the respective embodiments described above are easy to
pass the reliability evaluation test.
[0055] In the aforesaid embodiments (the semiconductor device 1 and
the semiconductor device 10), the DIL type semiconductor device
with the leads expanded in two directions from the package was
exemplified. But, the invention is not limited to it and can also
be applied effectively to a semiconductor device with the leads
expanded in one or four directions from the package and a
surface-mount type semiconductor device such as SMT
(surface-mounted device).
* * * * *